Control of combustion in in situ treatments of carbonaceous deposits



y 1965 w. c. SHELDON 3,194,311

CONTROL OF COMBUSTION IN IN SITU TREATMENTS OF United States Patent3,194,311 CONTROL OF COMBUSTION IN IN SITU TREAT- MENTS 0F CARBONACEOUSDEPOSITS Walter C. Sheldon, Englewood, Colo., assignor to Marathon OilCompany, a corporation of Ohio Filed Dec. 26, 1961, Ser. No. 162,211Claims. (Cl. 166-11) This invention relates to a treatment ofunderground reservoirs and more particularly relates to methods ofpreparing underground carbonaceous deposits for subsequent in situcombustion recovery treatments.

In situ combustion techniques for recovery of petroleurn values fromcarbonaceous deposits are well known in the art. They are frequentlyused for secondary recovery treatment of oil reservoirs when suchreservoirs can no longer be economically worked by conventional pumpingmethods. Such methods also are used for initial treatment of other typesof petroleum deposits when the viscosity of the material in a reservoiris too high for economical pumping operations. Such deposits may includetar sands and other reservoirs containing viscous petroleum liquids.

These latter deposits frequently occur in relatively thick formations.For purposes of this invention a relatively thick formation may bedefined as one that exceeds thirty feet in thickness; When treating suchrelatively thick formations or deposits by in situ combustionoperations, the upper portion of the deposit tends to burn or burns muchmore rapidly than its lower portions. This apparently is the result ofdifierences in density between the injected air and the hydrocarbons(oil) in place which causes a propagated flame front to spread upwardlyand outwardly, while downward movement is retarded; and undesirableoverburning of limited areas of the reservoir above the point of initialflame propagation occurs, resulting in loss of valuable petroleummaterial which otherwise might have been recovered.

It is an object of this invention to provide a simple, efiicient andeconomical method of treating relatively thick underground reservoirs inorder to condition or prepare them for controlled in situ combustionrecovery operations.

It is another object of the invention to provide a simple,

effiicient and economical method of preparatory treatment for a lowerportion of combustion zones in a carbonaceous deposit for providingbalanced or controlled in situ combustion throughout the upper and lowerportions thereof.

It is still another object of the invention to provide a simple,economical and efficient method of controlling the direction and rate ofadvance of the combustion front in in situ combustion operationsperformed in relatively thick petroleum reservoirs.

When using the method of controlling in situ combusion in carbonaceousdeposits according to this invention, for formation to be treated ispenetrated by a plurality of wells, and in the usual practice thesewells will'include an injection'well and one or more production wells.The production wells may be located in any of the conventional'or otherspacing pattern employed in recovery of crude oil by other secondarymethods. One such pattern is the inverted five-spot pattern in which asubstantially centrally located injection well has four production wellsspaced at substantially even intervals thereabout.

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As shown in the accompanying drawing, the injection well 1 and aplurality of production Wells 2a and 2b should be drilled downwardthrough substantially the entire depth of the formation 3 to be treated.A packer 4 is set in injection well 1 to separate the deposit 3 into twoparts. Preferably, packer 4 is located in relation to the permeabilityof the structure and in some instances two packers may be used atvertically spaced points in the well.

Casing 5 may be placed in injection well 1 to any desired depth, andcasing 6a and 6b preferably are provided for wells 2a and 2b,respectively. Preferably the casings are capped at the surface, andsupport one or a plurality of conduits. Conduits '7 and 7a are supportedin casing 5 to deliver fiuid (solution or air) to selected depths ininjection Well 1 and conduit 8a in casing 6a and conduit 8b in causing6b deliver the production material to the surface. In preparing foroperation, an aqueous solution of a suitable combustion catalyst or anoil soluble catalyst is injected through the injection well below thepacker or packers and introduced into the lower zones or portions of thedeposit to be treated. A catalyst is employed to serve one or both oftwo functions, i.e., to promote or control combustion and/or initiatecombustion by spontaneous combustion. The catalyst is introduced throughthe well as a solution so as to distribute it through the portions ofthe formation where combustion is to be controlled. After combustion isinitiated, the combustion front movement is controlled by the relativedistribution of air or other oxygen-containing gas.

In one procedure utilizing my invention, the catalyst system iscomprised of an aqeous solution of a suitable metal salt which isinitially injected into the deposit through the injection well below thepacker, and between packers if a plurality of packers is used, andthence into the surrounding formation. The pyrophoric material is thenformed in place from the injected solution by suitable treatment, suchas the introduction of hydrogen sufide to form a pyrophoric metallicsulfide when a pyrophoric material is desired. Under some circumstances,a pyrophoric material will not be desired, in which case an aqueoussolution of a suitable catalyst such as a metallic salt is injectedwithout further treatment. Thereafter, air is injected into the treatedarea. If pyrophoric ma terial has been utilized, spontaneous combustionresults from the air introduction. Where a non-pyrophoric catalyst isemployed, conventional ignition practices will be required.

As an example of utilizing a pyrophoric material, an

through an injection well, followed by the injection of a quantity ofhydrogen sulfide gas or hydrogen sulfide in natural gas. The FeCl andthe hydrogen sulfide react to form FeS and hydrogen chloride. When thisreaction is essentially complete, a quantity of dry air is injected,which causes spontaneous ignition of the FeS and thus propagation of acombustion front in the lower portion of the deposit. The quantity ofhydrogen sulfide which is injected is preferably in a stoichiometricexcess of that required for complete reaction of the iron chloride, orin excess of that required to completely react the FeCl solution abovedescribed.

The air injection is an important factor of the foregoing method ofinitiating the combustions front action. Since the catalyst used isinitially in an aqueous solution, the air flow must be continued untilsuch time as it is substantially dry in order for it to spontaneouslyignite.

a i Once combustion-has been initiated thequantity of air injected isdetermined by desired temperatures and'jrates of flame front movement.Further, by-use of suitable temperature sensitive probesor'thermocouples, together flow paths to the formation to be treated.Otherwise, multiple strings of tubing may be used. By useof suita-'; blepackers and selective perforation of the outer casing;

it is possible to initiate afiame front atany. of a plurality in anaqueous solution is passed" downwardly through the appropriate passageto the desired portions of the forma-.

tion. Next, hydrogen sulfide or hydrogen sulfide I in natural gas, ifsuch is required, is passed downwardly through the same passage asthecatalyst. air or other oxygen enriched gas is passed down through thefiow paths in quantities appropriate to maintain temperature and/or rateof frontal advance. a

In either of the foregoing described procedures, it is I sometimesdesirable'to leave the packer or packers in place since .it'yiel'ds agreater degree of'control over, the oper-.

Subsequently,

' may beavailed of within the spirit and scope 'of the invention asdefinedinth hereunto. appendedlclaims.

I claim:

1. YA method for controlling combustion'permeableundergroundcarbonaceous deposits, Whichcomprisesjm troducing acombustion catalyst through an injection well into ,a selectedlevelthroughout a permeable portion of such a depositbetwen said injectionwell and a production I well, directing oxygen-containing gas throughsaidiinjecof levels, In such an arrangement, the: catalytic material Vwell. p o a v 2.,1A method for controlling combustion in permeableunderground carbonaceousdeposits, which i comprisesuina troducing acombustion catalystrthrough an'injection welli 1 tion Well into theportion of said deposit containing the.

combustion catalyst in a quantity .su'fficient to initiate zones ofspontaneous combustiontherein, propagating a. combustion front movementfromthe spontaneousycombusion zones by 1 continued introduction ofoxygen-con raining gas into the selected level'of thepermeable portion,introducing oxygen containinga gas through a separated passage ins-aidinjection well into vanjadjoining level- V 'of the permeable:deposit'after. a predetermined interval for initiatinga combustionfront movementims aid adwjoining level. substantially,.simultaneouslywiththe first I combustion front movement, and removing evolvedprodmovements through thesproduction':

ucts of both frontal into {a selected levelthroughouta.permeable-portionof 'ation relative to the rates of airinjection to the'fla'me;

front.- Fromthe foregoing, it will beapparent that at least-somepermeability :is requiredin the deposit in whichjthein situ combustionoperation is to be .con-

ducted after preparation for treatment according to this invention It isto be understood that in lesspermeable formations, When necessary, sandfracturing. oro hydrofracturing techniques may be utilized 'as'apreliminary step in the treatment;

With processes according'to this invention; it is possible'for anoperator to treat relatively thick formations 'as defined hereinbeforeandto obtain balanced or selective control of heat front movement. andbeneficiation through the entire thickness of such formation. This maybe done "by initiating a .combustion frontadjacent the bottom of theformation and allowing the gravity dif ference between injected air oroxygen-enriched gases and thereservoir fluids to exert thecharacteristic property of causing flame or combustion frontpropagationupwardly and outwardly from the point of ignition. Alternatively,

it is possible. to initiate in situ combustion simultaneously at aplurality of levels in the same formation, and by conundergroundcarbonaceous deposits, which comprises 'in'-;

troclucing' a combustion catalyst through an injectiouiwell, into aselected.levelithroughout-apermeable portion of i such a deposit:between said injection well and a;produc-, tionwell, directingoxygen-containing gas throughsaid 1 injection .well into .the portion ofsaid deposit. containing 1 trolof'the' air or oxygen input to pluralityof flame or,

combustion fronts, to obtain'a controlled ?or balancedv from theformation; a

7 When combustion takes place concurrently in both combustion zones,uniform rate of advance isnot' required, and one. advance may be rapidand the-other quite new; Also, it is not necessary to maintain constant-temperatures'througha given zone, or uniform tempera-.

tur'e'sin the plurality of zones. Frontal movement is slow'when oxygensupply is low andincreases as more oxygen is-supplied Thus, control ofoxygen input may be regulated to establish'any desired condition in theoperation.

be used will include dimethyl zinc, cacodyl and hydrides; of phosphorus,boron and silicon. Another type of 'jspon-- taneous'reaction which maybe availed of is the reaction of chlorine onv finely divided antimony. VChanges. and modifications: of materials and procedures When spontaneous"heating. and eduction of variable petroleum constituents such a depositbetween said injection well and a production well, directingoxygen-containing gas throughsaid injec- =tion,introducinggoxygen-containing gas; through} a sepa-;combustioncatalystina quantity, sufficient,to'initiateizones' of thepermeable deposit after a predetermined period of .bustion frontmovement from thespontaneous' combustion zones by continued introduction;of oxygen-containing; gas

into the selected level of the 'permeable portion, introduce;ingoxygen-containing gas through a separated passage in said injectionWelljintoan adjoining overlaying level of:

the permeable depositafter a predetermined periodof combustionfrontpropagation at the selected level for initiating a combustion frontmovement insaid iadjoin-y ing level substantially simultaneously withthefirstcom; bustion front movement'andat adifferent;ratea-than' in saidselected level, and. removing evolved products of both.

frontal movements through'th'e, production well.

3. A method for controlling" combustion in permeable the combustioncatalyst ina :quantity suliicie'ntgto initiate zones. ofspontaneouszcomb'ustiontherein, propagating a" combustion frontmovementfroimthe spontaneous com-"'- -;bustion zones by continuedintroduction 'of ;oxygen=eontaining gas: into the: selectedlevel of thepermeable Per-: tion', introducing oxygen-containing;gasthronghalseparatedpassage in said injection well into. an adjoininglevel; of the permeable deposit after a predeterminedperiod ofcombustion front propagation .atr'the. isele'ected- :level; forinitiating a combustion front movement in I said adjoining +7 levelsubstantially simultaneonslywitlrthe 1first combus tion-front movement,controlling the rate ofcbmbustion ,frontpropagation at aselectedratefintherespective levels by introducing,- different quantitiesrofsimultaneous-oxy--= gen-containing. gas thereto, andremoving'evolvedproducts of both. frontalrnovements through thejproduction ;well..

zones of spontaneous combustion therein, propagating a combustion frontmovement from the spontaneous combustion zones by continued introductionof oxygen-containing gas into the selected level of the permeableportion, introducing oxygen-containing gas into an adjoining overlayinglevel of the permeable deposit after a predetermined period ofcombustion front propagation at the selected level for initiating acombustion front movement in said adjoining level substantiallysimultaneously with the first combustion front movement, maintainingsubstantially uniform rate of simultaneous combustion propagation at therespective levels by introducing more oXygen containing gas into thelower level than is introduced into the upper level, and removingevolved products of both frontal movements through the production well.

5. A method for controlling in situ combustion in relatively thickunderground carbonaceous deposits, which comprises penetrating apermeable portion of such a deposit With at least one injection well andat least one production well at horizontally distant locations,disposing a packer in one of said injection wells intermediate the topand bottom of the deposit, introducing a combustion catalyst throughsaid injection well into the permeable portion below the packer level,directing oxygen-containing gas through said injection well into theportion of the deposit containing the combustion catalyst in a quantitysuflicient to initiate spontaneous combustion therein, introducingoxygen-containing gas through a separated passage in said injection wellinto the permeable portion above the packer at a predetermined timeinterval after initiating combustion in the underlying portion thereofwhile continuing introduction of oxygen-containing gas into theunderlying portion, and removing evolved products of the combustion inboth levels through the production well.

6. A method for controlling in situ combustion in relatively thickunderground carbonaceous deposits, which comprises penetrating apermeable portion of such a deposit with at least one injection well andat least one production well at horizontally distant locations,disposing a packer in one of said injection wells intermediate the topand bottom of the deposit, distributing an aqueous solution ofpyrophoric forming metal throughout the permeable portion below thepacker level between the injection well and the production well, nextintroducing hydrogen sulfide gas into the permeable portion containingthe pyrophoric metal, directing oxygen-containing gas into the permeableportion containing the pyrophoric metal and hydrogen sulfide gas in aquantity sufficient to initiate spontaneous combustion in the materialpreviously introduced and establish a frontal advance therein,introducing oxygen-containing gas into the permeable portion above thepacker at a predetermined time interval after initiating combustion inthe underlying portion thereof, so as to initiate a frontal advance insaid upper level, and removing evolved products of the combustion inboth levels through the production well.

7. A method for controlling in situ combustion in relatively thickunderground carbonaceous deposits, which comprises penetrating apermeable portion of such a deposit with at least one injection Well andat least one production well at horizontally distant locations,disposing a packer in one of said injection wells intermediate the topand bottom of the deposit, distributing an aqueous solution of FeClthroughout the permeable portion below the packer level between theinjection well and the production well, next introducing hydrogensulfide gas into the permeable portion containing the FeCl directingoxygen-containing gas into the permeable portion containing the -FeCland hydrogen sulfide in a quantity sufficient to initiate spontaneouscombustion in the material previously introduced and establish a frontaladvance therein, introducing oxygen-containing gas into the permeableportion above the packer at a predetermined time interval afterinitiating combustion in the underlying portion thereof, so as toinitiate a frontal advance in said.

upper level, and removing evolved products of the combustion in bothlevels through the production well.

8. The method for controlling in situ combustion in relatively thickunderground carbonaceous deposits, which comprises penetratingsubstantially the entire depth of a permeable portion of such a depositwith at least one injection well and at least one production well athorizontally distant locations, disposing a packer in one of saidinjection Wells intermediate the top and bottom of the permeableportion, distributing an aqueous solution of FeCl;,, throughout theper-meable portion below the packer level between the injection well andthe production well, next introducing hydrogen sulfide in natural gasinto the permeable portion containing the FeCI directing dry air intothe permeable portion containing the 'FeCl and hydrogen sulfide in aquantity in a stoichiometric excess of that required to completely reactthe FeCl solution thereby initiating spontaneous combustion andestablishing a frontal advance in the permeable portion below the packerlevel, introducing oxygen-containing gas through a separated passageinto the permeable portion above the packer at a predetermined timeinterval after initiating combustion in the underlying portion so as toinitiate and maintain a simultaneous frontal advance in the upper level,and removing evolved products of both frontal movements through theproduction well.

9. A method for controlling in situ combustion in relatively thickunderground carbonaceous deposits, which comprises penetrating apermeable portion of such a deposit with at least one injection well andat least one production well at horizontally distant locations,disposing a packer in one of said injection Wells intermediate the topand bottom of the deposit, introducing a combustion catalyst throughsaid injection well and throughout the permeable portion below thepacker level, directing oxygen-containing gas through said injectionwell into the portion of the deposit containing the combustion catalystin a quantity suflicient to initiate spontaneous combustion therein,introducing oxygen-containing gas through a separated passage into thepermeable portion above the packer at a predetermined time intervalafter initiating combustion in the underlying portion thereof so as toinitiate a frontal advance in the upper level substantiallysimultaneously with the first combustion front movement, and removingevolved products of both frontal movements through the production well.

10. A method for controlling in situ combustion in relatively thickunderground carbonaceous deposits, which comprises penetrating apermeable portion of such a deposit with at least one injection well andat least one production well at horizontally distant locations,disposing a packer in one of said injection Wells intermediate the topand bottom of the deposit, introducing a combustion catalyst throughsaid injection well and throughout the permeable portion below thepacker level, directing oxygen-containing gas through said injectionwell into the portion of the deposit containing the combustion catalystin a quantity sufiicient to initiate spontaneous combustion therein,introducing oxygen-containing gas through a separated passage into thepermeable portion above the packer at a predetermined time intervalafter initiating combustion in the underlying portion thereof so as toinitiate a frontal advance in the upper level substantiallysimultaneously with the first combustion front movement, determining thecombustion front temperatures in the overlaying and underlying portionsunder treatment, varying the combustion front tempera- 61F. and rate ofadvance in each said portion by changing the input of oxygen-containinggas thereto, and removing evolved products of both frontal movementsthrough the production well.

(References on following page)

1. A METHOD FOR CONTROLLING COMBUSTION IN PERMEABLE UNDERGROUNDCARBONACEOUS DEPOSITS, WHICH COMPRISES INTRODUCING A COMBUSTION CATALYSTTHROUGH AN INJECTION WELL INTO A SELECTED LEVEL THROUGHOUT A PERMEABLEPORTION OF SUCH A DEPOSIT BETWEEN SAID INJECTION WELL AND PRODUCTIONWELL, DIRECTING OXYGEN-CONTAINING GAS THROUGH SAID INJECTION WELL INTOTHE PORTION OF SAID DEPOSIT CONTAINING THE COMBUSTION CATALYST IN AQUANTITY SUFFICIENT TO INITIATE ZONES OF SPONTANEOUS COMBUSTION THEREIN,PROPAGATING A COMBUSTION FRONT MOVEMENT FROM THE SPONTANEOUS COMBUSIONZONES BY CONTINUED INTRODUCTION OF OXYGEN-CONTAINING GAS INTO THESELECTED LEVEL OF THE PERMEABLE PORTION, INTRODUCING OXYGEN-CONTAININGGAS THROUGH A SEPARATED PASSAGE IN SAID INJECTION WELL INTO AN ADJOININGLEVEL OF THE PERMEABLE DEPOSIT AFTER A PREDETERMINED INTERVAL FORINITIATING A COMBUSTION FRONT MOVEMENT IN SAID ADJOINING LEVELSUBSTANTIALLY SIMULTANEOUSLY WITH THE FIRST COMBUSTION FRONT MOVEMENT,AND REMOVING EVOLVED PRODUCTS OF BOTH FRONTAL MOVEMENTS THROUGH THEPRODUCTION WELL.